Grant: Discovery Grants Program - Individual

The world's oil consumption will not peak until just before 2030 at the earliest, and oil will continue to be critical to the world's energy needs for many decades. Canada produces much of its oil through oil sand mining and extraction, a process that has generated billions of cubic meters of contaminated wastewater. Extraction, processing, and petroleum spills release harmful chemicals into the environment, including naphthenic acids and polycyclic aromatic hydrocarbons. Fundamental knowledge of how these substances exert toxicity on aquatic organisms is essential to prevent the release of harmful amounts of these substances and to diagnose the cause when adverse impacts on fish and wildlife are observed. This research will examine the hypothesis that such chemicals act on cells primarily through mitochondrial toxicity. Mitochondria are the energy-producing machines of cells that work through a process called oxidative phosphorylation that consumes oxygen. Impairment of this process leads quickly to cell death. Having previously established that naphthenic acids uncouple or disrupt oxidative phosphorylation in isolated mitochondria, this research will test whether these mechanisms can lead to the death of isolated liver cells. Compounds that act on functions such as oxidative phosphorylation that occur within fatty cell membranes often have low water solubility, which allows them to easily enter the membrane. An examination of whether toxicity and water solubility are related will be conducted using a suite of compounds structurally related to naphthenic acids. This relationship is important for predicting the effects of mixtures of substances in the environment. Following this, an examination of whether naphthenic acids cause toxicity to living fish through a mechanism mediated by mitochondria will be evaluated. The mechanisms of toxicity of polycyclic aromatic hydrocarbons to isolated fish mitochondria will be examined. In addition, several traditional and emerging toxicants similar in structure to naphthenic acids will also be examined for their potential to uncouple oxidative phosphorylation. The research will add to the emerging and growing body of research on the importance of mitochondria on toxicity, disease, and aging. Results will help inform critical regulatory decisions, such as what, if any, are safe levels of substances in oil sands wastewater for release.